1. Field of the Invention
The present invention generally relates to Universal Serial Bus (USB), and more particularly to an adaptive USB charging method and system.
2. Description of Related Art
According to Universal Serial Bus (USB) specification, a USB device connected to a host can sink at most 500 mA. Some USB devices even sink current from USB ports of a host (such as a personal computer) to charge the USB devices. Accordingly, charging regulations, such as Battery Charging Specification or APPLE USB Power Adaptor, are drafted to govern the device charging.
However, a conventional USB device can select only one USB charging mode to perform charging when the computer is in a hibernation mode or is shut down. When the USB device is removed and is replaced with another USB device supporting another USB charging mode, the replacing USB device either is incapable of being charged or just continues using the preceding USB charging mode.
Moreover, a conventional USB charging circuit is commonly manufactured as an external circuit. In other words, a user has to buy an extra USB charger, which increases expenses and causes inconvenience.
For the foregoing reasons, a need has arisen to propose a novel USB charging scheme for not only resolving unchangeable charging mode or unchargeability as mentioned above, but also decreasing circuit area.